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Komatsu PC300LC-3 has slow hydraulics

CJLennon ยท 2011-09-01 12:45

Hey Folks, as always, thanks to all for making me look smart. I have a Komatsu PC300LC-3 who upper carriage hydraulics all run very slow. The machine walks perfectly but the upper hydrualics (boon, arm, bucket, swing) all operate very slowly. My first thought is that both pumps are fine because the machine walks perfectly. But as I review the hydraulic diagram, I can't find anything in common that the upper body hydraulics (boom, bucket, arm, swing) have with each other but NOT with the travel. So, this one has me stuck. But I noticed there is that Straight Travel Valve that seems to be involved in both the travel and the upper body stuff. That is the only thing I can see that might be the problem. So, any takers on this one? Getting desperate. I'm too old to use the Hickory Highlift (i.e., shovel). As always, thanks for thinking about this one! Chris

Replies6
  1. #1jey_c2011-09-01 13:30

    check the pilot pressure and send feedback

  2. #2CJLennon2011-09-01 13:43

    Hey jey_c, thanks for the quick reply. Could bad pilot pressure affect upper carriage but not travel? Thanks!

  3. #3John C.2011-09-02 01:07

    As I recall the straight travel valve is operated by switches on the travel pedal spools under the cab. That valve joins both main valve flows together when you go into travel but the flows for the other functions are slowed down. Pull the front bottom guard under the cab and you should see the plungers. One or the other will get stuck in and the solenoid is always on shifting the spool. Good Luck

  4. #4CJLennon2011-09-02 07:06

    Jihn C., I owe you big time! Thanmks for the reply. I'll check it out and get back to you on what I find. Again, thanks! Chris

  5. #5IsaacEssex2011-09-20 14:23

    anyone have an opinion? what kinda production (CY/hr) can you get out of a pc300 loading off road trucks with clay/silt dirt if you are not elevated, sitting flat with the trucks, and digging down to 15 foot? i was guessing he could load out 200 CY/hr as long as i kept the trucks in front of him. any thoughts?

  6. #6Toyboy3b2011-09-21 04:35

    Have you ever had a hydraulic tune up done? they should be done at regular service intervals, it can make quite a difference. If you have a pump or pressure problem (main or pilot) the tune up procedure will find it.